infusion

Under one infusion one understands the administration of a liquid into the human body by bypassing the gastrointestinal system ("parenteral"), usually into a vein. The access route via an infusion is chosen either because the respective substance cannot be used in any other way, or because of factors affecting the patient such as e.g. B. a swallowing disorder.

What is an infusion?

From one infusion one speaks when the supply lasts for a long time. While the patient is sitting or lying down, the respective substance is supplied either under gravity control via an infusion bottle or via a mechanical infusion pump.

This is to be distinguished from an injection in which the active ingredient is introduced into the patient's body within a short period of time, for example by means of muscle power by applying pressure to the plunger of an injection syringe.

Intravenous access is predominantly chosen for infusions, i.e. the liquid is introduced directly into a vein. Other common approaches are subcutaneous (under the skin) or intraosseous (into the medullary cavity of a bone) infusion.

Function, effect & goals

A infusion of fluids is required when absorption through the gastrointestinal tract is not possible. This can be due to the fact that the respective substance is in principle not suitable for absorption through a mucous membrane.

Another reason may be that the patient in question cannot take a drug in this way due to his illness, which in principle could also be swallowed. The most common route for an infusion is the intravenous route, in which the fluid is introduced into a vein, which takes it to the heart and from there throughout the body.

The infusion can be administered either through a metal cannula or through a flexible indwelling venous cannula inserted into a superficial vein, typically in the hand or arm. If drugs are to be administered that easily irritate these superficial veins, or if a suitable vein cannot be found, the infusion can be into one of the central veins in the neck, under the collarbone, or in the groin.

One then speaks of a central venous catheter (CVC). A special form is a port catheter, in which a tube is surgically inserted into a central vein that is connected to a chamber that is implanted under the skin. By piercing the skin and a membrane on this chamber with a special needle, a patient can easily be infused again and again via a central venous access. Such a port catheter is used z. B. often for the infusion of chemotherapy drugs in patients with cancer.

For some purposes such as B. for the infusion of liquid in patients who cannot drink enough, the route of a subcutaneous infusion can be chosen. A fine needle is inserted into the fatty tissue under the skin. The advantage of this method is that there is no need to find a vein. The disadvantage is that the fluid is only slowly absorbed by the subcutaneous fatty tissue into the vascular system and that some drugs are not suitable for such a subcutaneous infusion.

In emergency situations, when parenteral medication is required but no vein is found, an intraosseous infusion can also be administered using a sturdy needle into the bone marrow cavity, e.g. B. the lower leg bone is introduced.

Risks & dangers

A infusion carries various risks. If air accidentally gets into the vascular system, it can lead to a life-threatening air embolism. There is also a risk if liquids that are not suitable for intravenous infusion are administered in this way.

After all, any substance introduced into the body can trigger an allergy, which can be particularly pronounced with parenteral infusion. If the port slips out of the vein, the infusion can get into the surrounding tissue instead of the vein, which can cause severe soft tissue damage with some drugs.

Finally, complications can arise when creating the access. A typical complilation when creating a CVC for an infusion is, for example, injury to the lungs from the puncture needle, which can lead to a lung collapse (“pneumothorax”).